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Coil inductance question

:: EPE Chat Zone ­:: ­Radio Bygones Message Board :: » EPE Forum Archives 2010 - » Archive through 05 May, 2011 » Coil inductance question « Previous Next »

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noel
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Username: noel

Post Number: 90
Registered: 06-2005

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Posted on Wednesday, 13 April, 2011 - 05:06 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Hi all,
I have a question someone may be able to help me with.

When using an inductance meter to measure the inductance of a solenoid coil, does the resistance of the coil have any significant effect on the inductance value of the coil ?

Take the following practical example:
Consider two solenoid coils produced with the same number of coils turns, but with two different wire sizes and hence two different resistance values. Both coils are sourrounded with the same steel frame.

Using an inductance meter and ignoring parctical tolerances on steel work, etc., would you expect the inductance of both coils to be the same ?

Thanks - Noel.
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pebe
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Username: pebe

Post Number: 64
Registered: 05-2005

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Posted on Wednesday, 13 April, 2011 - 07:16 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

It will depend on how the inductance is measured. If measured with a good bridge that can null out the resistance, then it will be no problem.

If the inductor's impedance is measured, then there could be an error because the measured impedance will be the vector sum of the Lz and R.

If the impedance is resonated in a tuned circuit then the resistance would make no practical difference.
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alec_t
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Username: alec_t

Post Number: 613
Registered: 03-2009

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Posted on Wednesday, 13 April, 2011 - 10:56 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Noel,
I wouldn't expect the inductance of both coils to be the same, because a main factor is the number of turns per unit length. Thicker wire means fewer turns per unit length (so lower inductance, for a given coil length). Also, thicker wire means a greater coil radius (another factor affecting inductance).

Alec
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noel
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Username: noel

Post Number: 92
Registered: 06-2005

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Posted on Friday, 15 April, 2011 - 03:22 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

pebe & alec_t: Thanks for your help

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